Abundance and Ecological Risk Assessment of Microplastics in Touristic Beaches along the Atlantic Coast of Lagos, Nigeria

The pervasiveness of microplastics (MPs) is a critical global issue that impacts negatively on almost all ecosystems. This study investigated MPs abundance, polymer types and their ecological risks in five major beaches (Landmark, Tarkwa bay, Elegushi, Lighter house and Oniru) along the Atlantic coast of Lagos, Nigeria. Beach sand and adjacent intertidal sediment samples were collected at five sampling points on each beach and MPs were recovered from them using supersaturated solution of zinc chloride (ZnCl2, density 1.5 g/cm³). The isolated MPs were enumerated with a stereomicroscope and classified according to their morphological features (shapes and colours). Average abundance ranged from 1278 ± 655 to 5688 ± 1377 MPs/kg in beach sands, and from 776 ± 214 to 2104 ± 1065 MPs/kg in the intertidal sediments. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy identified many single-use polymer types that resulted from food packaging and carrier bags, as well as non-single use ethylene vinyl acetate (EVA) polymer, associated with recreational facilities and gaming equipment used on the beaches. Ecological risk assessment revealed that all sampled points on each beach were “polluted” with MPs (Pollution Load Index ˃ 1). Risk quotient (RQ) values also indicated risks to organisms at 86% of the sampling points, where abundance exceeded a predicted no effect concentration (PNEC) value. Hazard index (HI), a measure of the MPs chemical toxicity, showed that the MPs might pose “high” to “extremely high” ecological toxicity at all the sampled points. The HI values were influenced mostly by MPs of polystyrene (PS), low density polyethylene (LDPE) and EVA types. Banning of single-use plastics should be enforced to reduce plastic pollution of the beaches and lessen the risks associated with MPs occurrence.